Fire-resistant open joint structure and its method

ABSTRACT

In an open joint structure for the prevention of water leakage an isobaric space is formed which has no difference between pressure in the space and ambient pressure. The open joint structure contains at least one groove 11 extending in the vertical direction formed on the exterior side of a vertical edge of a precast concrete curtain wall and which faces an opposing groove 11 of an adjacent precast concrete curtain wall. A heat barrier plate 10 with cutout portions on through holes 13 is mounted between the side walls in the grooves, thereby dividing the isobaric space into a fire-blocking isobaric space (A) between the exterior side of the wall and the heat barrier plate 10 and a radiant heat-blocking isobaric space (B) between the heat barrier plate 10 and a pair of preformed sealants 20, 20. This structure exhibits both a fire-resistant function and a watertight function in an open construction method.

FIELD OF THE INVENTION

The present invention relates to improvements in the open joint methodfor a precast concrete curtain wall and, more particularly, to thefire-resistant open joint structure and its method for joining. Inparticular, a vertical joint is adapted to make the precast concretecurtain wall thinner, that is, such a joint, particularly a verticaljoint, is formed between panels, a panel and a sash or a panel and astructural frame.

DESCRIPTION OF THE BACKGROUND ART

In recent years, a so-called open joint method has been adopted as awatertight method for precast concrete curtain walls. This open jointmethod is capable of smoothly discharging rainwater driven in through ajoint by having an opening with a gap of an appropriate width in thejoint so as to have an isobaric space therein. This isobaric space hasno pressure differential from the outside. Heretofore, as shown in FIG.11, a method has been adopted which uses a double seal method that isconstructed so as to prevent water from penetrating into the joint byfilling up the front portion of a joint S with a gun grade sealant (1)on to a backing material (2) and mounting a preformed elastic sealant(3) at the back of the joint to form a watertight layer. However, if thelife of the sealant is relatively shorter than that of the precastconcrete curtain wall or the like and defects occur in the seal (forinstance, interlaminar deviations or other problems), water driven inthrough the joint may created a pressure differential within the jointand thereby cause water leakage.

As shown in FIG. 12, the open joint method exhibits a watertight effectby an isobaric space BS. The isobaric space, however, is open to theexterior so that it may become a passage through which fire flames couldenter. In this case, only a wind barrier (5) mounted at the back of thejoint is not satisfactory for fire-resistant performance so that theexterior walls need to be thick enough for fire resistance. Inparticular, the vertical joint is not provided with a flashing (6) as isused in a horizontal joint, as shown in FIG. 13. Thus, the improvementsfor the vertical joint in fire-resistant performance are restricted. Ofcourse, as shown in FIG. 11, such fire-resistant performance can beprovided on the vertical joint if a fire-resistant material (4) would befilled in the joint. It is to be understood, however, that this losesthe meaning of the open joint method which utilizes the isobaric space.

OBJECT OF INVENTION

The present invention has an object of providing a fire-resistant openjoint structure and its construction method designed to providefire-resistant performance while maintaining a watertight effectachieved by the open joint method without becoming an obstacle to theconstruction of the open joint method, in view of the current situationin which the open joint method is being adopted in the construction ofprecast concrete curtain walls and the like. Such an open jointstructure will create the starting point for making a thinner wallplate.

As a result of extensive studies on open joint systems with the goal ofobtaining both fire-resistant properties and watertight properties, thepresent invention was completed on the basis that a fire could beblocked completely without hindering the functions originated from theisobaric space in the open joint method by dividing an isobaric spaceformed outside a wind barrier in a vertical joint by mounting a heatbarrier plate with through-holes in the joint into front and rearspaces. The first isobaric space is designed so as to be capable ofblocking a fire between the exterior side of the exterior wall and theheat barrier plate, on the one hand, and the second isobaric space isdesigned so as to be capable of blocking radiant heat from the heatbarrier plate between the heat barrier plate and the wind barrier by wayof convection caused in the air layer. Thus, rainwater penetratingthrough the joint from outside the exterior wall is blocked by the firstand second isobaric spaces and the heat barrier plate dividing the twospaces. Fire is furthermore blocked by the fire-blocking action of theheat barrier plate and the air convection action in the second isobaricspace.

The fire-resistant open joint structure according to the presentinvention is characterized, as shown in FIG. 1(d), in that, in the openjoint structure capable of preventing water from penetrating into theprecast concrete curtain wall joint by forming an isobaric space with nopressure differential from the outside, the vertical edge of one precastconcrete curtain wall (panel W) is provided with at least one groove 11in the vertical direction. This groove 11 on the exterior side of thejoint faces an opposing groove 11 formed likewise on the adjacent panel.A heat barrier plate 10 with cutout portions 13 on the side portionsthereof is mounted so as to bridge the side walls of the grooves and apair of preformed sealants 20 and 20 are mounted on the facing verticaledges of the walls at the back of the joint between the panels W,thereby forming an isobaric space for blocking a fire between theexterior side of the curtain wall panel and the heat barrier plate 10 aswell as for forming an isobaric space for the blocking of the radiantheat between heat barrier plate 10 and a pair of the preformed sealants20 and 20.

It is preferred to use as the heat barrier plate 10 a continuous metalplate having a flange portion 12 formed by bending both sides of theplate. The flange portion is provided with cutout portion 13 as shown inFIG. 2. However, while cutout portions 13 are indicated in FIG. 2, it iscontemplated that through-holes may also be used in the flange portions12.

It is also preferred that the preformed sealant 20 be a sponge gasket inthe form of a hollow rod and having a fire-resistant property.

The fire-resistant open joint structure according to the presentinvention is further characterized, as shown in FIGS. 1(a) to 1(d),inclusive, in that the open joint method is carried out by mounting thepreformed sealant at the back of the vertical edge of the precastconcrete curtain walls, panels W, W, and by constructing the precastconcrete wall panels W, W with the positioning grooves 11 formed on theexterior sides of the vertical edges so as to extend in the verticaldirection and to face each other on the exterior side of the joint andso as to abut the preformed sealant 20 of the precast concrete wall Wwith a preformed sealant 20 mounted on the adjacent precast concretewall W to form a second seal. The heat barrier plate 10 having cutoutportions or through-holes 13 between the positioning grooves 11 and 11arranged facing each other in the vertical joint between the precastconcrete wall panels, thereby forming a fire-blocking isobaric space (A)between the outside of the panels and the first seal 10 and a radiantheat-blocking isobaric space (B) between the first seal 10 and thesecond seal 20.

A plurality of heat barrier plates 10 may be mounted in the positioninggrooves 11 in the front-to-rear order as the first seal 10 (FIG. 3).

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

FIGS. 1(a) to 1(d), inclusive, are each a diagrammatical viewillustrating the steps of the construction of the fire-resistant openjoint method according to the present invention;

FIG. 2 is a perspective view illustrating a heat barrier platepreferable in performing the fire-resistant open joint method accordingto the present invention;

FIG. 3 is a cross sectional view illustrating a variation of thevertical joint structure shown in FIG. 1(d);

FIG. 4 is a partially sectional, perspective view illustrating thevertical joint structure of the open joint structure according to thepresent invention;

FIG. 5 is a partially sectional, perspective view illustrating thedetail of installation of the vertical joint structure;

FIGS. 6(a) and 6(b), respectively, are a side elevation and a plan viewrepresenting the installation details indicating the actual dimensions;

FIG. 7 is a diagrammatical view describing the fire-resistant action;

FIG. 8 is a graph comparing the fire-resistant effect attained by thejoint constructed by the fire-resistant and watertight open joint methodaccording to the present invention with that attained by a joint withoutany fire-resistant and watertight treatment;

FIGS. 9(a) and 9(b), respectively, are cross sectional viewsillustrating the fire-resistant open joint structure according to thepresent invention and an open joint structure used for comparisonpurposes;

FIG. 10 is a graph showing watertightness performance;

FIG. 11 is a diagrammatical sectional view illustrating a conventionalfire-resistant open joint structure;

FIG. 12 is a cross sectional view illustrating a vertical jointstructure formed by the conventional open joint method; and

FIG. 13 is a perspective view illustrating a horizontal joint structureformed by the conventional open joint method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The fire-resistant open joint structure according to the presentinvention may be constructed by the following procedures.

As shown in FIG. 1(a), a curtain wall panel W is formed with a preformedsealant 20 mounted at the back of on vertical edge. This preformedsealant 20 acts as a wind barrier. A positioning groove 11 extending inthe vertical direction of the edge is formed on the exterior side of thejoint. Exterior curtain wall panels such as precast concrete panels(hereinafter referred to as "PC panels") W and W are constructed by aconventional open joint method. For instance, as shown in FIG. 1(b), aPC panel W is pulled between the PC panels placed on both sides thereofand set near the position where it is installed. With a fastenermounted, the level and the surface are adjusted and then a secondaryfastener on the PC panel side is connected to a primary fastener on theside of the structural frame with bolts and nuts.

More specifically, as shown in FIGS. 5, 6(a) and 6(b), a T-shaped anchorplate 32 embedded in and fixed to the upper portion of the lower wallpanel W is installed to a support plate 31 extending from a beam 30 ofthe H-section with an adjustable bolt 33 and a washer 34 with aneccentric hole. The level adjustment is conducted with a level adjustingbolt 35. On the other hand, an anchor plate 36 embedded at the lowerportion of the upper wall panel W is connected to a Z-shaped steel plate38 through an insert 37 so as to cause the Z-shaped steel plate 38 tocome in mesh with the projection of the embedded T-shaped anchor plate32. This allows the Z-shaped steel plate 38 to install the wall panel Win a manner to permit swaying in the horizontal directions with smallswinging motions caused by middle-size earthquakes and the adjustablebolt 33 is installed in a manner to be locked against large shockscaused by big earthquakes.

Turning now to FIG. 1(c), the preformed sealants 20 and 20 are securedlyabutted with each other at the back of the vertical joint to form thesecondary seal as a wind barier, and the positioning grooves 11 and 11of the wall panels are adjacent to each other and extend in the verticaldirection at the front of the joint.

The isobaric space BS formed on the exterior side of the joint in frontof the second seal is then divided into front and rear spaces byinserting the first seal from the top so as to bridge between thepositioning grooves 11 and 11 which face each other. As shown in FIG. 2,the first seal is constituted by a heat barrier plate, for example, aheat barrier plate 10 of a continuous thin stainless steel with flangeportions 12 formed by folding both sides thereof and forming cutoutportions 13. While FIG. 2 shows only cutout portions, it is contemplatedthat through-holes may also be formed in flange portions 12. As shown inFIG. 1(d), the isobaric space BS is provided with the first isobaricspace (A) for blocking fire between the exterior side of the wall paneland the first seal and the second isobaric space (B) for blockingradiant heat between the first seal and the second seal.

Referring now to FIG. 3, the heat barrier plate 10 as the first seal maybe mounted each in pairs of the positioning grooves 11 and 11 formed ina line on the edges of the adjacent PC wall panels. A spaced formed bythe positioning grooves 11, 11 and the heat barrier plate 10 should beensured as an isobaric space in order to avoid a reduction in thepressure therein. A gap formed by the heat barrier plate 10 and thepositioning grooves 11, 11 should also be ensured to not be closed bymovement of the heat barrier plate 10 mounted in the grooves 11, 11 orby rainwater entering into the grooves 11, 11.

It is preferred to finish the inside of the wind barrier 20 by mountinga non-combustible joint material 40 as shown in FIG. 4.

In the fire-resistant and watertight joint structure constructed by theopen joint method as described above, fire coming from outside theexterior concrete wall panel W can be blocked by the heat barrier plate10 from entering into the second isobaric space (B) on the rear portionof the joint, as shown in FIG. 7. Furthermore, although radiant heatextends from the heat barrier plate 10 to the second isobaric space (B)between it and the second seal 20, the radiant heat is absorbed by anair layer in the space and discharged to the outside by means of aconvection phenomenon, thereby exhibiting an action of heat discharge.Such fire-resistant effects were confirmed by the following tests. Thatis, a phenomenon of a decrease in temperatures of fire outside PC panelswas followed where a heat barrier plate 10 is mounted in the frontpositioning groove 11 of the thin PC panel and where no heat barrierplate is mounted therein. The results are shown in FIG. 8. It will befound from the results that the temperatures near the preformed sealant20 reached about 600° C. in instances where no heat barrier plate isinserted, while the temperatures near the preformed sealant 20 droppedto about 300° C. or lower in instances where the heat barrier plate 20is inserted.

It is noted that, in the structure as described above, rainwater entersinto the first isobaric space (A) as it hits on the exterior side of thecurtain wall, but it hits on the heat barrier plate 10, thereby fallingalong the surface of the heat barrier plate 10.

The rainwater hit on the heat barrier plate 10 which is likely to enterinto the rear space through gaps between the heat barrier plate 10 andthe positioning groove 11 (as splashes or the like) is caused to dropdown the wall portion of the positioning groove 11 without any suctionforce occurring because the second isobaric space (B) is formed of arelative length so as not to create any difference in the atmosphericpressure from the first isobaric space (A) by way of the cutout portionsor through-holes 13 formed on the flange portions 12 of the heat barrierplate 10. For instance, even if rainwater could enter into the secondisobaric space (B), it will not reach the preformed sealants 20 and 20constituting a rear wind barrier.

The watertight effect was tested by the following procedures.

As equipment for testing the watertightness of the vertical jointstructure of PC panels formed in accordance with the present invention,there were made a plate having flange portions with cutout portions, asshown in FIG. 9(a), and a plain plate without any flange portion havingcutout portions, as shown in FIG. 9(b). Tests for the watertight effectswere then determined in the following manner.

As shown in FIG. 10, the embodiment shown in FIG. 9(a ) does not greatlyincrease the pressure difference ΔP between the ambient pressure Po andthe pressure Pz in the second isobaric space (B) formed between thefirst seal 10 and the second seals 20 as a gap percentage between thesecond seals 20, 20 increases. And the pressure differential does notexceed a threshold pressure differential for a limit on water leakage(usually 7 to 10 kg f/m² at the maximum wind pressure of 300 kg f/m²) ina range in which the PC panel swings even if the gap percentage wouldvary to a great extent, thus preventing water leakage from the secondseals. On the contrary, the embodiment shown in FIG. 9(b) does vary to agreat extent with an increase in pressure differentials P between theambient pressure Po and the pressure Pz in the second isobaric space(BS) formed between the first seal 14 and the second seals 20 as the gappercentage changes and the pressure differential in a range of values inwhich gap percentages should be set exceeds the threshold pressuredifferential, whereby water leakage may occur from the second seals 20.

Therefore, the embodiment of FIG. 9(a) having the heat barrier platewith flange portions with cutout or through-holes used to divide thespace into the first isobaric space A and the second isobaric space Bhas more water leakage prevention ability than the embodiment shown inFIG. 9(b) with a baffle 14 employed. When using the embodiment of FIG.9(a), the thickness of the precast concrete panel can be made thinner.

As will be apparent from the above description, the present inventionprovides a first isobaric space (A) between the exterior side of thecurtain wall panel and the first seal, which can block fire by the heatbarrier plate of a continuous length, and the second isobaric space (B)between the first and second seals, which can block radiant heat fromthe first seal by the convection of an air layer. This constructionleads to the complete blocking of rainwater driven in through the jointfrom the exterior side of the curtain wall panel by the first and secondisobaric spaces and the heat barrier plate partitioning the spaces forhaving the fire blocking effect of the heat barrier plate and theconvection action of the air layer in the second isobaric space. Asconventional joint methods have the shortcoming of providing a ratherpoor fire resistant design, the present invention overcomes suchobstacles of prior art methods and provides a joint structure having apredetermined degree of fire resistance while enabling a thinner curtainwall to be used. Moreover, the present invention exhibits desiredfire-resistant and watertight effects without difficulty even if thewalls are rendered thinner, so that it becomes the starting point ofmaking an exterior precast concrete curtain wall a thinner plate. It isalso to be noted that, since the heat barrier plate used for the presentinvention becomes a substitute for a fireproof insulating material usedin conventional methods, the present invention does not demonstratedrawbacks of a decrease in fire-resistant performance due to leakagefrom the fireproof insulating material caused by sealing defects arisingfrom an interlaminar displacement or the like, as in conventionalmethods. It is further to be noted that the construction work for theopen joint method according to the present invention is rendered verysimple because the heat barrier plate can be inserted after the build-upof curtain walls.

Although the present invention has been described by making referencesto the vertical joint structure of PC curtain walls as an embodiment, itis needless to state that it can be applied likewise to metal curtainwalls and GRC curtain walls. Furthermore, like construction can, ofcourse, be applied to horizontal joints.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

We claim:
 1. A fire resistant open joint structure for a wall made froma plurality of wall sections, each of said wall sections having verticaledges along at least two sides thereof, a first one of said verticaledges of one wall section being placed proximate to a second verticaledge of another wall section to form said wall, each of said wallsections having an exterior side and an interior side, said open jointstructure comprising:at least one vertical groove formed in said firstvertical edge; at least one vertical groove formed in said secondvertical edge, said groove of said first edge facing said groove of saidsecond edge when said wall sections are placed proximate one another; apreformed sealant positioned on an interior side of each of saidvertical edges of said wall sections, sealant on said first verticaledge abutting sealant on said second vertical edge when said wallsections are placed proximate one another; a heat barrier plateextending between said groove of said first vertical edge and saidgroove of said second vertical edge to form two isobaric spaces, saidfirst isobaric space being disposed on one side of said plate andextending to the exterior side of said wall sections, said secondisobaric space being disposed on the other side of said plate andextending in a direction toward the interior side of said wall sectionsto abutting sealants, said first isobaric space forming a fire-blockingisobaric space whereby a fire on the exterior side of said wall can beblocked by said heat barrier plate, said second isobaric space forming aradiant heat-blocking isobaric space whereby radiant heat from saidfirst isobaric space can be discharged, said first and second isobaricspaces therefore aiding in fire-resistance, said heat barrier platehaving two vertically extending edges which are folded for giving saidplate a generally U-shaped cross section, said plate being of acontinuous length along said vertical grooves; and communication meanson said heat barrier plate for permitting said first isobaric space tobe in communication with said second isobaric space, said communicationmeans further preventing rainwater from leaking through said jointstructure thus forming a watertight joint structure, said communicationmeans comprises cutout portions located along the folded edges of saidheat barrier plate, said cutout portions aiding in preventing suctionfrom being created when rainwater enters the joint structure and runsdownwardly thereby maintaining said joint structure watertight.
 2. Thefire-resistant open joint structure as recited in claim 1, wherein saidsealants on the interior sides of each of said vertical edges are asponge gasket formed in a hollow rod shape.
 3. A fire resistant openjoint structure for a wall made from a plurality of wall sections, eachof said wall sections having vertical edges along at least two sidesthereof, a first one of said vertical edges of one wall section beingplaced proximate to a second vertical edge of another wall section toform said wall, each of said wall sections having an exterior side andan interior side, said open joint structure comprising:at least onevertical groove formed in said first vertical edge; at least onevertical groove formed in said second vertical edge, said groove of saidfirst edge facing said groove of said second edge when said wallsections are placed proximate one another; a preformed sealantpositioned on an interior side of each of said vertical edges of saidwall sections, sealant on said first vertical edge abutting sealant onsaid second vertical edge when said wall sections are placed proximateone another; a heat barrier plate extending between said groove of saidfirst vertical edge and said groove of said second vertical edge to formtwo isobaric spaces, said first isobaric space being disposed on oneside of said plate and extending to the exterior side of said wallsections, said second isobaric space being disposed on the other side ofsaid plate and extending in a direction toward the interior side of saidwall sections to abutting sealants, said first isobaric space forming afire-blocking isobaric space whereby a fire on the exterior side of saidwall can be blocked by said heat barrier plate, said second isobaricspace forming a radiant heat-blocking isobaric space whereby radiantheat from said first isobaric space can be discharged, said first andsecond isobaric spaces therefore aiding in fire-resistance, said heatbarrier plate having two vertically extending edges which are folded forgiving said plate a generally U-shaped cross section, said plate beingof a continuous length along said vertical grooves; and communicationmeans on said heat barrier plate for permitting said first isobaricspace to be in communication with said second isobaric space, saidcommunication means further preventing rainwater from leaking throughsaid joint structure, thus, forming a watertight joint structure, saidcommunication means comprises through-holes located along the foldededges of said heat barrier plate, said through-holes aiding inpreventing suction from being created when rainwater enters the jointstructure and runs downwardly thereby maintaining said joint structurewatertight.
 4. A fire resistant open joint structure for a wall madefrom a plurality of wall sections, each of said wall sections havingvertical edges along at least two sides thereof, a first one of saidvertical edges of one wall section being placed proximate to a secondvertical edge of another wall section to form said wall, each of saidwall sections having an exterior side and an interior side, said openjoint structure comprising:two vertical grooves formed in said firstvertical edge; two vertical grooves formed in said second vertical edge,said grooves of said first edge facing said grooves of said second edgewhen said wall sections are placed proximate one another; a preformedsealant positioned on an interior side of each of said vertical edges ofsaid wall sections, sealant on said first vertical edge abutting sealanton said second vertical edge when said wall sections are placedproximate one another; a heat barrier plate extending between a firstone of said two grooves of said first vertical edge and a first one ofsaid two grooves of said second vertical edge to form two isobaricspaces, said first isobaric space being disposed on one side of saidplate and extending to the exterior side of said wall sections, saidsecond isobaric space being disposed on the other side of said plate andextending in a direction toward the interior side of said wall sectionsto abutting sealants, said first isobaric space forming a fire-blockingisobaric space whereby a fire on the exterior side of said wall can beblocked by said heat barrier plate, said second isobaric space forming aradiant heat-blocking isobaric space whereby radiant heat from saidfirst isobaric space can be discharged, said first and second isobaricspaces therefore aiding in fire-resistance; communication means on saidheat barrier plate for permitting said first isobaric space to be incommunication with said second isobaric space, said communication meansfurther preventing rainwater from leaking through said joint structure,thus, forming a watertight joint structure; and a second heat barrierplate extending between a second one of said two vertical grooves ofsaid first vertical edge and a second one of said two vertical groovesof said second vertical edge.